What does a spherical mass with smooth regular borders and anechoic interior likely indicate in ultrasonography?

A spherical mass with smooth, regular borders and anechoic interior typically indicates a simple cyst in ultrasonography.

In sonographic imaging, a simple cyst is characterized by a well-defined, smooth outline and a completely fluid-filled center that appears anechoic, meaning that it does not reflect ultrasound waves and therefore shows up as dark on the image. These features are consistent with a benign lesion, as malignant tumors usually present with irregular borders and may contain solid or heterogeneous components.

The clarity and uniformity of a simple cyst's shape, along with the absence of internal echoes or septations, further support the diagnosis. These factors differentiate it from other conditions such as complex cysts, which may have multiple internal echoes or irregularities, or malignancies, which tend to have invaded the surrounding tissue, leading to an irregular appearance.

Overall, the description aligns well with what is clinically categorized as a simple cyst, making it the most appropriate interpretation in this context.